End-eXpiratory Occlusion Test to Predict fluId REsponsiveness in the Operating Room (EXPIRE)

"A set of respiratory and hemodynamic measurements (including cardiac output) will be recorded at each stage:~* T0: baseline.~* T1: At the end of the first EEO (15 sec or 30 sec)~* T2: 1 minute after completion of the first EEO. Return to baseline.~* T3: At the end of the second EEO (15 sec or 30 sec)~* T4: 1 minute after completion of the second EEO. Return to baseline.~* T5: Before the fluid challenge test (4 ml/kg of 0.9% saline over 5 min)~* T6: 1 minute after the end of the fluid challenge~A first set of measurements will be performed after intubation (before the surgical incision) and will be repeated, if necessary, in case of further decrease in stroke volume during surgery or in case of any clinical indication of volume expansion (i.e., arterial persistent hypotension, major hemorrhage, etc.)."